This invention relates to a colour picture tube provided with a slot type colour selection electrode. More particularly, it relates to an exposure apparatus for exposing to light phosphor films of a colour picture tube having a fluorescent screen composed of stripe-shaped phosphors or films of non-luminous substance coated between stripe-shaped phosphors of the so-called black matrix type colour picture tube.
There are many types of colour selection electrodes for use in colour picture tubes such as dot type, stripe type and slot type. In a colour picture tube incorporated with a slot type colour selection electrode it is not sufficient to form the phosphor to have dimensions and configurations which correspond to the slots formed in the effective area of the colour selection electrode. More particularly, when considering the landing error of the electron beams transmitting through respective slots it is necessary to form the phosphor in the form of continuous stripes extending in the longitudinal direction of the slots. To form such phosphor it has been proposed to use exposure apparatus provided with a plurality of collimeters which are juxtaposed in the direction of the slots or a collimeter provided with an elongated light source. With these exposure apparatus, however, an image of a mercury arc lamp or of the collimeter itself tends to appear in the exposure light so that it is difficult to obtain a desired brightness distribution on the inner surface of the panel on which the fluorescent screen is to be formed. Especially, in the latter type exposure apparatus, since there is a limit on the length of the linear light source it is impossible to perform satisfactory exposure. Such difficulty is especially remarkable in the so-called black matrix type colour picture tube wherein the deviation in the brightness determines most of the white uniformity.